Climate Thermal Load Based Minimum Flow Rate Water Pump Control

ABSTRACT

A control system for minimizing the flow rate and energy consumption of a water pump in a vehicle. The control system and method correlate a climate thermal load value with the temperature of the coolant in a climate control cooling circuit. A correlation is performed by mapping the inputs to a desired pump flow rate that is determined to be necessary at a minimum to provide adequate cooling for the engine and for air conditioning or heating the vehicle.

TECHNICAL FIELD

This disclosure relates to a system for controlling a water pump in avehicle to minimize the flow rate and reduce power consumption.

BACKGROUND

Conventional internal combustion engines have a water pump that isdriven by an accessory belt. Water pump flow varies with engine speedand is calibrated to provide ample cooling at maximum power. Accessorybelt drive systems add weight that reduces fuel economy.

Current hybrid engines use water pumps that are driven by accessory beltdrives on the battery charging internal combustion engine. An auxiliarywater pump is required to heat the passenger compartment when thebattery charging internal combustion engine is not operating. Auxiliarywater pumps add weight to the vehicle that also reduces fuel economy.

SUMMARY

This disclosure proposes a control system for a hybrid vehicle having aprimary water pump that is driven by an electric motor. This disclosuremay also relate to other types of vehicle drives that are driven by anelectric motor instead of an accessory belt, such as an all-electricvehicle. The cooling system integrates a climate thermal load value thatis provided by the vehicle bus and a heater coolant temperature value.Data from these values is mapped to generate a heater core flow requestvalue that sets the pump flow rate.

Accessory belt drives may be eliminated by providing air conditioningsystems and power steering systems that are driven by electric motors.Further power savings are achieved by minimizing the water pump flowrate to a rate that is sufficient to meet climate thermal loadrequirements. As vehicles become more efficient, the effects ofparasitic losses become more important.

The climate thermal load value is a composite calculated value that isprovided by the climate module on the vehicle electrical control systembus. The climate thermal load value may be based upon the temperatureset point of the passenger compartment heating, ventilation and airconditioning (HVAC) control in the passenger compartment, the outside orambient air temperature, the coolant temperature, and other factors suchas sun load.

According to one aspect of the disclosed system for controlling a waterpump in a vehicle, an electric motor is provided that operates the waterpump. A controller generates a heater core flow request signal as afunction of a climate thermal load value and a heater coolanttemperature value. The controller determines whether the heater coreflow request is greater than zero and provides a signal to the motor toset the pump flow rate to satisfy the heater core flow request.

According to other aspects of the system, the determining step mayinclude selecting a pump flow rate based upon the table of valuescorresponding to a plurality of climate thermal load values and aplurality of heater coolant temperature values. The climate thermal loadvalue is based, in part, upon the cabin set point and ambient airtemperature. The heater coolant temperature may be obtained from athermal sensor that senses the temperature of the coolant, for example,at an inlet to the heater core. Alternatively, the coolant temperaturemay be inferred from a cylinder head temperature sensor. The pump flowrate is selected to minimize power consumption by the electric motor andincrease fuel economy. The controller determines whether a HVAC selectoris set at a maximum defrost setting that causes the pump flow rate to beset at a maximum value. The controller also determines whether an HVACselector is requesting cabin temperature modification.

According to another aspect of this disclosure, a method is provided forcontrolling an electric water pump in a vehicle. The method includes thesteps of determining whether a maximum defrost input is actuated andsetting the water pump at maximum flow. Next, the HVAC input may beactuated if the maximum defrost input is not actuated and setting thewater pump is set to “no flow” if the HVAC input is not actuated. If theHVAC input is actuated, a climate thermal load value and a heatercoolant temperature value are obtained. The climate thermal load valueand heater coolant temperature value are integrated in a multiplevariable table to develop a heater core flow rate. The heater core flowrate is mapped to a pump speed if the heater core flow rate is greaterthan the threshold value.

According to other aspects of the method, the threshold value for theheater core flow rate may be zero. The HVAC input includes a thermistorfor sensing cabin temperature and a variable temperature selector switchfor controlling the temperature of the passenger compartment.

According to another aspect of the method, the integrating step mayinclude selecting a heater core flow rate based upon a table of valuescorresponding to a plurality of climate thermal load values and aplurality of heater coolant temperature values. The climate thermal loadvalue is based, in part, upon the cabin temperature set point andambient air temperature. The heater core flow rate is selected tominimize power consumption by the electric motor and increase fueleconomy.

According to another aspect of the disclosure, a heating, ventilationand air conditioning system is provided for a vehicle having an electricmotor driven water pump. The system comprises a heater core, an HVACselector having a heat request seating, an air cooling request setting,a defrost setting, and a maximum defrost setting. The climate controlmodule provides a thermal load value. A coolant temperature sensormeasures the temperature of a coolant. A controller provides a coolantflow request value to the water pump. When the maximum defrost settingis actuated, the coolant flow request is set at maximum. When the heatrequest setting is off and the air cooling request setting is zero, theheater cool flow rate is set based upon the thermal load value and thecoolant temperature value. If the heater core flow rate is greater thanzero, the heater core flow is mapped to the water pump speed.

According to another aspect of the HVAC system, the controller mayselect the coolant flow request based upon a table of valuescorresponding to a plurality of climate thermal load values and aplurality of coolant temperature values. The heat request setting andthe air cooling request setting are compared to a passenger compartmentthermistor signal for controlling the temperature of a passengercompartment. The controller integrates a table of values correspondingto a plurality of climate thermal load values and a plurality of heatercoolant temperature values.

These and other aspects of the present invention will be betterunderstood in view of the attached drawings and the following detaileddescription of the illustrated embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of a cooling circuit for a vehicle;

FIG. 2 is a flowchart illustrating the steps of the method and operationof a water pump control system; and

FIG. 3 is a table for integrating the plurality of thermal load valueswith a plurality of engine coolant temperature values to select aminimum heater core flow request.

DETAILED DESCRIPTION

Detailed descriptions of the illustrated embodiments of the presentinvention are provided below. The disclosed embodiments are examples ofthe invention that may be embodied in various and alternative forms. Thefigures are not necessarily to scale. Some features may be exaggeratedor minimized to show details of particular components. The specificstructural and functional details disclosed in this application are notto be interpreted as limiting, but merely as a representative basis forteaching one skilled in the art how to practice the invention.

Referring to FIG. 1, a combustion engine 10 is shown with a water pump12 that is driven by an electric motor 14. The engine 10 may be abattery charging engine for a hybrid electric vehicle. The engine 10 andwater pump 12 are part of a radiator cooling circuit generally indicatedby reference numeral 16 that circulates water and antifreeze through aradiator 18 to cool the engine 10. Prior to reaching a predeterminedtemperature, the water may flow through a bypass 20 to a thermostat 22.Upon reaching the predetermined temperature, the coolant is directed tothe radiator 18. Gas is separated from the coolant in a de-gas reservoir24. The fluid recirculates through the radiator coolant return 26 fromeither the radiator 18 or the de-gas reservoir 24 and returns it to thethermostat 22.

The engine 10 and water pump 12 are also connected to a climate controlcircuit generally indicated by reference numeral 28 that provides thecoolant to an exhaust heat recovery/coolant preheat apparatus 30 and aheater core 32. The exhaust heat recovery/coolant preheat apparatus 30may circulate coolant around exhaust system components to recover heatfrom the exhaust system. The heater core 32 provides warm air forheating a passenger compartment 33 through air ducts represented by thedashed line in FIG. 1. A heater core inlet coolant temperature sensor 34senses the temperature of the coolant in the climate control coolingcircuit 28. The coolant in the climate control cooling circuit 28returns the coolant to the thermostat 22 in a closed loop.

Referring to FIG. 2, a control system and method are shown as aflowchart. The control system and method start at 42. In a first step,at 44, the system determines whether a maximum defrost request has beenselected by a vehicle occupant at a selector control panel 43. If theuser has requested a maximum defrost request, the coolant flow formaximum defrost is requested at 46. If the maximum defrost request isnot selected at 44, the system looks for a climate modification requestat 48. The climate modification request is made by a vehicle occupantoperating an HVAC selector control panel 43 having selector switchesthat may be provided in many forms. The selector switch may be a digitaltemperature selection, a knob on a potentiometer, or the like. If aclimate modification request is not made by a vehicle occupant, nocoolant flow is requested at 50.

If there is a climate modification request, at 48, the coolant systemcontroller 49 reads the thermal load value from the climate module at52. The thermal load value is obtained from an electrical bus 53 in thevehicle. The thermal load value is a composite value based upon theselector control panel 43, thermistor input 45 and ambient airtemperature sensor 55. Other inputs to the thermal load value may be asun sensor 57, a temperature setting, or other inputs. The heatercoolant temperature is obtained, for example, from a thermal sensor 34(shown in FIG. 1) that senses the temperature of the coolant at an inletto the heater core 32, or may sense the temperature of the cylinder headtemperature (CHT) from which the coolant temperature may be inferred.The coolant temperature may also be sensed at other locations in theclimate control cooling circuit 28 (shown in FIG. 1). The controller 49also reads the engine coolant temperature (ECT), at 54. The ECT isobtained from the heater core inlet coolant temperature sensor 34 (shownin FIG. 1). The ECT may be inferred from another sensor, such as theCHT.

The heater core flow request is determined as a function of the thermalload value and the engine coolant temperature. A heater core flowrequest is generated by the controller 49 at 56. At 58, the heater coreflow request is compared to zero to determine if the flow is greaterthan zero. If the flow is not greater than zero, the system returns tostart. However, if the flow is greater than zero, a signal is providedin the controller 49 to map the heater core flow to a pump flow value at60.

Referring to FIG. 3, a multi-variable map, or “look-up table”, is shownin which the ECT is mapped against the thermal load value. Dependingupon the thermal load and engine coolant temperature, one of 16 flowrates may be selected that is provided to the electric motor 14 (shownin FIG. 1) to control the flow rate of the water pump 12 (shown in FIG.1).

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms of the invention. Rather,the words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the invention.Additionally, the features of various implementing embodiments may becombined to form further embodiments of the invention.

What is claimed is:
 1. A system for controlling a water pump in avehicle comprising: an electric motor operating the water pump; acontroller generating a heater core flow request signal as a function ofa climate thermal load and a heater coolant temperature; and providing asignal to the motor to set the pump flow rate to satisfy the heater coreflow request.
 2. The system of claim 1 wherein the determining stepincludes selecting a pump flow rate based upon a table of valuescorresponding to a plurality of climate thermal load values and aplurality of heater coolant temperature values.
 3. The system of claim 1wherein the climate thermal load value is based upon the cabintemperature set point, and ambient air temperature.
 4. The system ofclaim 1 wherein the heater coolant temperature is obtained from athermal sensor that senses the temperature of the coolant at an inlet toa heater core.
 5. The system of claim 1 wherein the pump flow rate isselected to minimize power consumption by the electric motor andincrease fuel economy.
 6. The system of claim 1 wherein the controllerdetermines whether a heating ventilation and air conditioning (HVAC)selector is set to a maximum defrost setting and wherein the pump flowrate is at a maximum value.
 7. The system of claim 1 wherein thecontroller determines whether an HVAC selector is requesting cabintemperature change.
 8. The system of claim 1 wherein the climate thermalload value is obtained from a vehicle bus.
 9. A method of controlling awater pump in a vehicle comprising: setting the water pump at maximumflow if a maximum defrost input is actuated; if the maximum defrostinput is not actuated, setting the water pump to no flow if the HVACinput is not actuated; if the HVAC input is actuated, integrating aclimate thermal load value and a heater coolant temperature value usinga multiple variable table to select a heater core flow rate, and if theheater core flow rate is greater than a threshold value, providing asignal to an electric motor that controls the flow rate of the waterpump.
 10. The method of claim 9 wherein the threshold value is zero. 11.The method of claim 9 wherein the HVAC input includes a thermistor and avariable temperature selector switch for controlling the temperature ofa passenger compartment.
 12. The method of claim 9 wherein theintegrating step includes selecting a heater core flow rate based upon atable of values corresponding to a plurality of climate thermal loadvalues and a plurality of heater coolant temperature values.
 13. Themethod of claim 9 wherein the climate thermal load value is based uponthe cabin temperature set point, and ambient air temperature.
 14. Themethod of claim 9 wherein the heater core flow rate is selected tominimize power consumption by the electric motor and increase fueleconomy.
 15. A heating ventilation and air conditioning (HVAC) systemfor a vehicle having an electric motor driven water pump, the systemcomprising: a heater core; an HVAC selector having a heat requestsetting, an air cooling request setting and a maximum defrost setting; aclimate module that provides a thermal load value; a coolant temperaturesensor that determines the temperature of a coolant; a controller thatprovides a coolant flow request value to the water pump, wherein thecoolant flow request is set to a maximum if the maximum defrost settingis actuated, wherein the coolant flow request is set at zero if the heatrequest setting is off, and a heater core flow rate is set based uponthe thermal load value and coolant temperature value; and wherein if theheater core flow rate is greater than zero, the heater core flow ismapped to the water pump speed.
 16. The system of claim 15 wherein thecontroller selects the coolant flow request based upon a table of valuescorresponding to a plurality of climate thermal load values and aplurality of coolant temperature values.
 17. The system of claim 15wherein the heat request setting and the air cooling request setting iscompared to a passenger compartment temperature signal for controllingthe temperature of a passenger compartment.
 18. The system of claim 15wherein the controller integrates a table of values corresponding to aplurality of climate thermal load values and a plurality of heatercoolant temperature values.
 19. The system of claim 15 wherein thecoolant temperature sensor is a cylinder head temperature sensor fromwhich the temperature of the coolant is inferred.
 20. The system ofclaim 15 wherein the thermal load value is based upon a cabintemperature sensor signal, a cabin temperature set point, an ambienttemperature signal, and a sun load sensor signal.